[mythtv] [mythtv-commits] Ticket #1805: Backend not responding, with backtrace and log

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Sat May 13 05:25:51 UTC 2006

f-myth-users at media.mit.edu wrote:
>     Date: Fri, 12 May 2006 20:47:25 -0700
>     From: Jim Westfall <jwestfall at surrealistic.net>
>     MythTV <mythtv at cvs.mythtv.org> wrote [05.13.06]:
>     > #1805: Backend not responding, with backtrace and log
>     > -------------------------------------+--------------------------------------
>     >  Reporter:  tom at redpepperracing.com  |       Owner:  ijr
>     >      Type:  defect                   |      Status:  new
>     >  Priority:  minor                    |   Milestone:     
>     > Component:  mythtv                   |     Version:     
>     >  Severity:  medium                   |  
>     > -------------------------------------+--------------------------------------
>     >  The symptom that I have been experiencing is that the backend will all of
>     >  a sudden stop  responding to connection requests. The process is still
>     >  running, and it's not eating CPU, but neither a frontend nor mythweb can
>     >  connect to the backend. I finally managed to get a backtrace and backend
>     >  log when it happened.
>     > 
>     >  Version:
>     >  root at mythtv:/var/log# mythbackend --version
>     >  Library API version: 0.19.20060331-1
>     >  Source code version: 9918
>     >  Options compiled in:
>     >   linux debug using_lmsensors using_v4l using_oss using_alsa using_ivtv
>     >  using_lirc using_x11 using_xv using_xrandr using_frontend using_backend
>     > 
>     >  Machine is an AMD Sempron 2200, 512MB RAM, 2xPVR-250.
>     > 
>     >  See attached backtrace and backend log from around where it happened. I
>     >  was experimenting with de-interlace and XvMC settings, so I was going in
>     >  and out of live tv a number of times just before it happened. Not sure if
>     >  that is related. It also seems to happen around the turn of the hour when
>     >  a couple of recordings start. Also of note is that the recordings continue
>     >  to actually record until I stop and restart the backend process, and
>     >  resume when it comes up.
>     > 
>     I assume you have a slave backend too?  
>     Looking at the backtrace (your master backend?) it appears to have a lock 
>     on the socket that is waiting for a slave backend to respond about 
>     generating a pixmap.  At the same time the main app thread is trying to 
>     process a customEvent, which is blocked trying to get the lock on the 
>     same socket.  The main app thread being blocked like this is likely 
>     causing all qt event processing to stop.
> Interesting.
> Is this likely to work the same in 18.1?  At least once a month,
> I have a similar lockup, in a setup with one MBE and one combined
> FE/SBE.  Communication between the FE and the MBE just hangs.  At
> the same time, MythWeb stops being able to serve pages (they
> eventually just time out).  There hasn't been much of a pattern
> to it, except that I don't think it tends to happen -unless- I'm
> doing UI operations pretty much at the same time.  (Obviously,
> this is something of a heisenbug, since I can't -tell- that the
> lockup has happened unless I -am- trying to use the UI... :)
> I'm reasonably sure that the MBE continues to be able to continue
> recording in-progress shows, and even starts recording new ones,
> in the hung state (though I'm not 100% sure of this recollection).
> So I wind up having to wait until there's no activity in the
> recordings directory, and then boot the MBE, and -then- I also
> have to boot the FE/SBE, since booting the MBE invariably screws
> up the FE/SBE no matter why I booted the MBE.  (E.g., once I boot
> the MBE, the MBE thinks that the SBE's tuners are unavailable and
> won't schedule recordings on them, and sometimes (usually?) the
> FE can't even talk to the database, either, although I may be
> misremembering that latter part.  Booting the FE/SBE fixes the
> problem of unavailable tuners; is this behavior still prevalent
> in 19?)
> P.S.  Unlike the OP, I'm doing absolutely nothing fancy with video;
> my FE is just spitting SD video out the TV-out of a PVR-350.  Also,
> my hangs have nothing to do with LiveTV, which I almost never use.
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I have the same thing but because I have  3 SBE running, the first MBE 
restart usually will not pickup any of the SBE tuners. It will list the 
names but none of the tuners will show-up. If I restart the MBE again it 
will then find one SBE set of tuners (random) and then I have to restart 
the other SBE(s) to have the master see it's tuners.

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